Total knee prosthesis

ABSTRACT

This prosthesis of the knee permits the tibial pivoting movements with due consideration for the two types of rotation, i.e. the systematic inward rotation accompanying the knee flexion and stretching, and the free rotation which can take place only after about 20* of flexion from the normal position of the tibia, the latter being inclined outwards in the stretched knee position, with respect to the thigh-bone extension.

[ 1 Oct. 10,1972

United States atent Bousquet et a1.

1,122,634 5/1956 France.....................128/92 C [54] TOTAL KNEE PROSTHESIS bert, Lyon, both of France [73] Assignee: Association de LEcole Catholique for Arthroplasty of the Knee," by H. H. Young; Journal of Bone and Joint Surgery, Vol. 45A, No. 8, Dec. 1963, pages 1627- 1642.

dArts et Matiers de Lyon, Lyon, France [22] Filed: Jan. 29, 1971 Primary Examiner-Richard A. Gaudet 1 Appl' 0950 Assistant Examiner-Ronald L. Frinks Attorney-Waters, Roditi, Schwartz & Nissen [30] Foreign Application Priority Data Jan. 30, 1970 [57] ABSTRACT This prosthesis of the knee permits the tibial pivoting movements with due consideration for the two types of rotation, i.e. the systematic inward rotation accompanying the knee flexion and stretching, and the free rotation which can take place only after about 20 of flexion from the normal position of the tibia, the latter being inclined outwards in the stretched knee position, with respect to the thigh-bone extension.

France......................7003234 [52] US. 128/92 C [51] Int. 1/24 [58] Field of Search..3/l, 22; 128/92 R, 92 C, 92 CA [56] References Cited UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS 3,506,982 Steffee...............................3/l

6 Claims, 6 Drawing Figures 163,476 6/1958 Sweden....................128/92 C s 5: in

PATENTEHucI 10 m2 SHEET 2 or 2 FiG.6

TOTAL KNEE PROSTHESIS FIELD OF THE INVENTION This invention is directed to a total prosthesis of the human knee.

The design of a prosthesis of the knee must take into account two essential factors, namely the knee flexion and the rotation of the tibia about its axis, as normally observed in the knee function. Now these two factors are closely connected. No knee flexion can take place without a tibial rotation. Admittedly, complete knee prostheses now proposed provide only the flexion stretching movements. Nevertheless, the importance of the tibia rotation should be regarded as an essential element for it permits of absorbing the greater portion of the stress exerted on the femoral and tibial anchoring rods of prostheses having only one type of movement.

Under these conditions, it is obvious that the tibial rotation reduces considerably the possibility of loosening the femoral and tibial rods and also of causing ulcers in the femoral bone cortex. Moreover, it enables periarticular muscles to operate under conditions approximating normal conditions.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide prosthetic means permitting the tibial rotation with due consideration of the two types of tibial rotation normally occurring in a human leg, i.e.

a. the systematic inward rotation accompanying the knee flexion and stretching movement, which is maximum (of the order of 6) during the first 30 of the flexion movement, then lower (of the order of 4 from 30 to 60 of the flexion movement), and finally zero (from 60 to 120).

b. the free rotation which can take place only after about 20 of flexion and is of the order of 8 (outwards only) from a 20 to 30 flexion, then of the order of 15 outwards and inwards, from the normal tibia position and with due consideration for the systematic rotation as per (a) hereinabove, when the flexion value ranges from 30 to 120.

Finally, in the prosthesis according to this invention due consideration is paid to the fact that in the stretched knee condition the tibia is inclined outwardly through an angle of the order of 10 in relation to the thigh-bone extension.

To this end, the complete knee prosthesis according to this invention comprises two members pivotally interconnected and provided with opposed rods for fastening and sealing these members to the lower end of the thigh-bone and to the upper end of the tibia, respectively, and with bearing plates ensuring a proper distribution of stresses throughout the cross-sectional area of the thigh-bone and tibia, ischaracterized in that the articulation consists of a spherical or ball-joint element rigid with the upper member fastened to the thigh-bone and engaging a part-spherical concavity of a socket rigid with the lower member fastened to the tibia, means, being provided for producing the systematic inward rotation of the tibia about its axis during the antero-posterior knee flexion, other means being provided for limiting to the desired angular values the free part-rotational movements, both inwards and outwards, of the tibia about its axis, complementary means being also provided for maintaining the tibia in a normal angular position in relation to the thigh-bone in the stretched leg position.

Advantageously, secured to the front edge of the bearing plate of the upper member fastened to the thigh-bone is a guide plate formed with an external groove inclined by 10 to the rod rigid with the upper member, the function of said groove consisting in properly guiding the patella or kneecap.

According to a simplified form of embodiment of this invention, the means provided for producing the systematic inward rotation of the tibia about its axis during the anteroposterior knee flexion comprise on the one hand a spindle extending diametrally through said spherical or ball-joint element rigid with the upper member the projecting, trunnion-forming portions of this spindle engaging bearing forming elongated apertures formed perpendicularly thereto in lateral upstanding flanges of the lower member which in the operative condition of the assembly are disposed on either side of said spherical element, and on the other hand a guide stud rigid with the part-spherical concavity of said socket and projecting radially into a groove having an at least partially helical configuration which is formed in the surface of said spherical element along an angle approximating 120 about the spindle extending through this spherical element, to permit the knee flexion through the normal amplitude Thus, the reaction of said stud in the groove of said spherical element, on the one hand, and the reaction of the spindle extending through said spherical element and engaging said bearing-forming elongated apertures, on the other hand, are effective for causing a systematic rotation of the tibia through an amplitude and in a direction subordinate to the enveloping angle of the groove formed in said spherical element.

According to a typical form of embodiment permitting of approaching with the mechanism of this prosthesis the kinetics of a human knee, the groove formed in said spherical element rigid with the thighbone member comprises three successive sections, namely a first section extending along the first 30 with a gradient of the order of 6, an intermediate following or second section of about 30, having a gradient of the order of 4, and finally an end or third section covering the last 60 with a zero gradient.

According to another feature characterizing this invention the means for limiting the free inward and outward rotational movements of the tibia about its axis to the desired values comprise a boss formed on the bearing plate of the upper member fastened to the thighbone, on either side of the portion interconnecting said plate and said spherical element, said boss being normally engaged between the edges of the ends of said upstanding flanges supporting the trunnion-forming portions of the diametral spindle which project from said spherical element, the clearance provided between each end of said boss and the relevant flange determining the value of the permissible free rotation.

Finally, according to another feature characterizing this invention and in order to comply with the normal angular relationship between the thigh-bone and the tibia in the stretched knee position the spindle extend ing diametrally through the spherical element is inclined by with respect to the axis of the rod rigid with the upper member of the prosthesis, so that in the hereto, illustrating by way of example a typical form stretched knee position the tibia axis is inclined by about 10 outwards in relation to the imaginary downward extension of the thigh-bone axis.

BRIEF DESCRIPTION OF THE DRAWINGS In any case the present invention will be better understood as the following description proceeds with reference to the diagrammatic drawings attached of embodiment of the prosthesis according to the invention. In the drawings:

FIG. 1 is a diagram showing the kinematics of the prosthesis as seen in side elevational view FIG. 2 is a front view corresponding to FIG. 1 but showing the tibia and thigh-bone angular relationship, in the case of the left-hand leg or knee FIGS. 3 and 4 are perspective views of the prosthesis members secured to the thigh-bone and tibia, respectively FIG. 5 is an axial section showing the complete prosthesis in the stretched-knee position and FIG. 6 is a cross section taken along the line 6-6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, showing the kinematics of the prosthesis according to this invention, the thighbone is illustrated in the form of a vertical straight line 2 and the tibia by another straight line 3 adapted to pivot angularly between two limit positions 3a and 3b, illustrated in dash and dot lines, with respect to the thigh-bone 2, these positions forming an angle of 120 to l30 with each other.

As shown in FIG. 1 the tibia 3a, in the stretched knee position, is slightly inclined forwards by about 3 with respect to the imaginary downward extension of the thigh-bone 2.

The systematic rotation of tibia 3 is that accomplished internally about the axis OZ during the first 60 of the knee flexion, i.e. during the rotation of the tibia 3 about the axis OX from position 3a to position 3c. The free rotation of the tibia is a rotation permitted about the axis 02 within the limits set forth in the foregoing.

It may be noted that the prosthesis should be so designed as to prevent any rotational movement of the tibia about the axis OY perpendicularto axes OX and OZ.

FIG. 2 shows how in the stretched position the tibia 3a must form an angle of about with the downward extension 2a of thigh-bone 2.

' FIG. 3 shows in perspective the upper member 4 of the prosthesis, i.e. the member to be fastened to the thigh-bone. This member 4 comprises a bearing plate 5 adapted properly to distribute the stress throughout the thigh-bone cross-sectional area, a rod 6 adapted to be sealed in the medullary canal of the thigh-bone, a guide plate 7 secured to the front edge 5d of plate 5, and having formed in its front surface a groove 7a adapted to guide the patella or the kneecap.

If a patellectomy or removal of the kneecap cannot be avoided, the guide plate 7 may be replaced by another, thicker guide plate adapted to compensate the loss of thickness due to the absence of patella while reducing the loss of strength of the quadriceps as a consequence of this patellectomy.

On its lower face the plate 5 carries a boss 8 serving a purpose to be explained presently this boss has secured thereto a spherical element 9 somewhat offset to the rear with respect to the rod 6 and receiving diametrally therethrough a spindle 11 forming an angle of about with the axis of rod 6. In this spherical element 9 a groove 12 surrounding the spindle concentrically through an angle of about to is formed; this groove 12 comprises three successive sections 12a, 12b and 120 having different gradients, namely a lower section 12a extending along 30 circa and having a gradient of about 6, an intermediate section 12b extending along the next 30 with a gradient of the order of 4, and finally an upper section 12c covering the last 60 or 70 but without any gradient.

FIG. 4 illustrated in perspective the lower member 13 of the prosthesis, i.e. the member to be secured to the upper portion of the patients tibia. This member 13 comprises a bearing plate 14 also adapted to ensure a proper distribution of stress throughout a cross-sectional surface of the tibia and formed with a hole 14a for receiving a fastening rod 15 to be sealed in the patients tibia.

The rear portion of the upper surface of plate 14 has formed therein a part-spherical bearing concavity 16 adapted to be engaged by the spherical element 9 of upper member 4 a stud 17 projecting from this partspherical concavity 16 is adapted to engage the groove 12 of spherical element 9. On either side of this partspherical concavity 16 is a flange 18 the two flanges 18 are each formed with an elongated aperture 19 adapted to act as a bearing to one of the trunniomforming projecting ends of the spindle 11 extending diametrally through spherical element 9.

The 10 angular relationship mentioned hereinabove with reference to FIG. 2 and obtaining in the stretchedleg position is obtained through-a corresponding and proper inclination of spindle 11 to the axis of rod 6.

The main members 4 and 13 of the prosthesis are assembled to each other before the surgical operation.

FIGS. 5 illustrates the prosthesis after this operation, in the stretched knee position.

As clearly seen in this Figure the axes of thigh-bone 2 and tibia 3, which may be considered as merging into the axes of rods 6 and 15, are not exactly co-extensive in that the axis of rod 15 is offset forwards by about 3 with respect to the downward extension of the axis of rod 6. This angular difference with respect to a simply aligned relative position between the axes 2 and 3 (FIG. 1) improves the knee stability in the stretched position. In this position, the lower edge of guide plate 7 acts as an abutment due to its engagement by the front edge of lateral flanges 18.

Since the bearings of spindle l1 consist of the elongated apertures 19 perpendicular to the longitudinal axis of tibia 3, the tibia can pivot in either direction about its axis until the spindle l1 abutes against the ends of said apertures 19. It is thus clear that with this arrangement the tibia 3 can rotate about its axis since, furthermore, the stud 17 is secured radially with respect to the mutually-engaged part-spherical bearing concavity 16 and spherical element 9. Besides, this arrangement is provided with a view to permit the systematic and free rotational movements of the tibia about its axis.

The systematic rotation is due on the one hand to the engagement of stud 17 in groove 12 and on the other hand to the engagement of the trunnion-forming ends of spindle lll in the elongated apertures 19 in fact, during the knee flexion, that is, when member 13 rotates about the spindle 11, the gradient of sections 12a and 12b of groove 12 tends to increase the angular position of tibia 3, but spindle 11 engaging the elongated apertures 19 counteracts this tendency and produces consequently the inward rotation of tibia 3 as a compensation for the impossibility of increasing its angular shift. This rotation is caused by the relative sliding movements of apertures 19 and spindle 11, the latter remaining stationary.

As will be readily understood, during the first 30 portion of this flexion the above-defined rotation is maximum since at that time the stud 17 engages the most inclined section 12a of groove 12. Then the rotation is reduced during the next 30 of the flexion movement, as the stud 17 engages the less inclined section 12b of groove 12. Finally, during the 60 to 70 last degrees of the flexion movement this systematic rotation is zero since the stud 17 engages the diametral section 120 of groove 12, which has no gradient at all.

As illustrated in FIG. 6 the boss 8 carried by bearing plate 5 of upper member 4 is partially engaged between the front edges of flanges 18 of the lower member 13, and a predetermined functional clearance is provided between each end of boss 8 and the corresponding flange 18. The purpose of this clearance is to limit the rotation of flanges 18 about the center of spherical element 9. Under these conditions it is possible, by giving an accurate value to each one of these clearances (which may vary with the knee flexion) to limit within the desired values the free, inward and outward rotational movements of the tibia.

Normally, the free inward rotation must be zero during the first 30 of the flexion movement. Therefore, as long as the flexion is less than 30, the operative clearance between the outer flange 18 and boss 8 must be strictly limited to that necessary for the systematic rotation. Under these conditions and considering this systematic rotation no play should exist or develop between the boss 8 and the outer flange 18, until the tibia has cleared the 30 limit. Beyond this 30 flexion some clearance must be available to permit the inward rotation to an extent of the order of 5. Besides, as the free outward rotation is of the order of 8, up to 30 of tibia flexion, the operative clearance provided between the boss 8 and the inner flange 18 must be such as to permit this 8 rotation with due consideration for the systematic rotation. Beyond 30, this clearance must increase to permit a outward rotation, still considering the systematic inward rotation;

Of course, this invention should not be construed as being strictly limited to the single form of embodiment of the prosthesis described and illustrated herein by way of example, since many modifications and variations may be brought thereto without departing from the basic principles of the invention as set forth in the appended claims.

What is claimed as new is:

1. Complete prosthesis for the knee, of the type comprising two respectively upper and lower members pivotally interconnected and each provided with a rod permitting the sealing of these members to the lower end of the thigh-bone and to the upper end of the tibia, respectively, each member aforesaid having a longitudinal axis and being provided with a transverse bearing plate adapted properly to distribute the stress throughout the cross-sectional area of said thigh-bone and tibia, wherein the pivotal interconnection comprises a spherical element rigid with the upper member and engaging a part-spherical bearing concavity formed in said lower member, means for producing the systematic inward rotation of the lower member about its said axis during the antero-posterior flexion of the knee, other means for limiting to the desired values the free inward and outward movements of rotation of said lower member about its said axis, and third means adapted to impart the normal angular position between said lower and upper members as compared to the tibia in relation to the thigh-bone in the stretched-leg position.

2. Prosthesis as set forth in claim 1, wherein the front edge of the upper member bearing plate has secured thereto a guide plate formed with an external groove inclined by 10 in relation to the axis of the rod of the upper member and adapted to guide the patella.

3. Prosthesis as set forth in claim 1, wherein the means for producing the systematic inward rotation of the lower member about its axis, during the anteroposterior flexion of the knee, comprise a spindle extending diametrally through said spherical element rigid with the upper member, the projecting portions of said spindle acting as trunnions and engaging bearingforming elongated apertures formed perpendicularly to said axis in upstanding lateral flanges rigid with said lower member, said flanges being disposed on opposite sides of said part-spherical concavity, and a guide stud carried by said concavity projecting radially into a groove formed with an at least partially helical configuration in said spherical element through substantially about the spindle extending through said spherical element, to permit the knee flexion with the normal amplitude.

4. Prosthesis as set forth in claim 3, wherein said groove formed in the spherical element comprises three successive sections, namely a first section extending along the first 30 and having a gradient of the order of 6, a second or intermediate section covering the next 30 and having a gradient of the order of 4, and finally a third section extending along the last 60 with a zero gradient.

5. Prosthesis as set forth in claim 4, wherein said means for limiting to the desired values the free inward and outward rotational movements of said lower member about its axis consist of a boss formed on said bearing plate having ends extending to opposite sides of said spherical element, said boss being normally engaged between the front edges of the ends of the upstanding flanges supporting the spindle extending diametrally through said spherical element, the clearance provided between each end of said boss and the corresponding lateral flange determining the value of the permissible free rotation.

6. Prosthesis as set forth in claim 5, wherein the normal angular relationship between the lower and upper members, in the stretched knee position, is maintained by said spindle disposed diametrally through said spherical element being inclined by an angle of 80 in relation to the axis of the rod rigid with the upper member, in order to impart in the stretched-knee position an outward inclination of about 10 to the tibia axis with respect to the downward extension of the thigh- 5 bone axis. 

1. Complete prosthesis for the knee, of the type comprising two respectively upper and lower members pivotally interconnected and each provided with a rod permitting the sealing of these members to the lower end of the thigh-bone and to the upper end of the tibia, respectively, each member aforesaid having a longitudinal axis and being provided with a transverse bearing plate adapted properly to distribute the stress throughout the cross-sectional area of said thigh-bone and tibia, wherein the pivotal interconnection comprises a spherical element rigid with the upper member and engaging a part-spherical bearing concavity formed in said lower member, means for producing the systematic inward rotation of the lower member about its said axis during the antero-posterior flexion of the knee, other means for limiting to the desired values the free inward and outward movements of rotation of said lower member about its said axis, and third means adapted to impart the normal angular position between said lower and upper members as compared to the tibia in relation to the thigh-bone in the stretched-leg position.
 2. Prosthesis as set forth in claim 1, wherein the front edge of the upper member bearing plate has secured thereto a guide plate formed with an external groove inclined by 10* in relation to the axis of the rod of the upper member and adapted to guide the patella.
 3. Prosthesis as set forth in claim 1, wherein the means for producing the systematic inward rotation of the lower member about its axis, during the antero-posterior flexion of the knee, comprise a spindle extending diametrally through said spherical element rigid with the upper member, the projecting portions of said spindle acting as trunnions and engaging bearing-forming elongated apertures formed perpendiCularly to said axis in upstanding lateral flanges rigid with said lower member, said flanges being disposed on opposite sides of said part-spherical concavity, and a guide stud carried by said concavity projecting radially into a groove formed with an at least partially helical configuration in said spherical element through substantially 120* about the spindle extending through said spherical element, to permit the knee flexion with the normal amplitude.
 4. Prosthesis as set forth in claim 3, wherein said groove formed in the spherical element comprises three successive sections, namely a first section extending along the first 30* and having a gradient of the order of 6*, a second or intermediate section covering the next 30* and having a gradient of the order of 4*, and finally a third section extending along the last 60* with a zero gradient.
 5. Prosthesis as set forth in claim 4, wherein said means for limiting to the desired values the free inward and outward rotational movements of said lower member about its axis consist of a boss formed on said bearing plate having ends extending to opposite sides of said spherical element, said boss being normally engaged between the front edges of the ends of the upstanding flanges supporting the spindle extending diametrally through said spherical element, the clearance provided between each end of said boss and the corresponding lateral flange determining the value of the permissible free rotation.
 6. Prosthesis as set forth in claim 5, wherein the normal angular relationship between the lower and upper members, in the stretched knee position, is maintained by said spindle disposed diametrally through said spherical element being inclined by an angle of 80* in relation to the axis of the rod rigid with the upper member, in order to impart in the stretched-knee position an outward inclination of about 10* to the tibia axis with respect to the downward extension of the thigh-bone axis. 